The production of silica-filled rubber mixtures requires a clearly higher mixing effort in comparison with rubber mixtures filled with carbon black. On the other hand, the greater mixing effort could in principle be avoided if the silica could be coagulated with the rubber latex immediately after production of the latter. However, the precipitation silicas currently employed for the production of tires are not readily suitable for this process, since for the most part they remain in the aqueous phase in the course of coagulation.
U.S. Pat. No. 5,166,227 describes a process for the production of emulsion-rubber mixtures filled with silica, in which a dispersion of silica and a rubber latex are spray-dried jointly. This process has the disadvantage that the entire quantity of water has to be vaporized in energy-intensive manner.
U.S. Pat. No. 4,757,101 describes a process for the production of free-flowing powdered elastomers filled with silica, in which silica is precipitated with a rubber latex. In this case other silicas are employed with rubber latices for other fields of application without sulfurous silyl ethers.
U.S. Pat. No. 2,727,876 describes rubber mixtures consisting of a large number of rubber types and esterified silicas.